Conventionally, there are practically used chairs provided with reclining functions for tilting backrests backward so that seated persons can take tilted postures and/or lying postures.
FIG. 6(a) and FIG. 6(b) show side views of a conventional chair. The chair is provided with: a horizontal seat 100; a standing backrest 101; and a shaft 103 that pivotally and swingably supports the seat 100 and the backrest 101.
On the other hand, when taking the chair, a seating person puts his/her thighs 103 and waist 106 on the seat 100, and learns his/her body 108 against the backrest 101. As a result, lower legs 104 hang down from the front of the thighs 103 centering on knees 105, and the waist 106 is located near the shaft 103.
In the example of FIG. 6(a), a head 109 is located in a position slightly higher than the backrest 101. The fulcrums of the thighs 107 are greater trochanters 107 located at positions separated from the shaft 103.
When the seated person or his/her nursing attendant reclines the backrest 101 from the standing posture as shown in FIG. 6(a), the backrest 101 changes its posture into the tilted posture as shown in FIG. 6(b). Herein, since the greater trochanters 107 are separated from the shaft 103, the upper body, including his/her head 109, of the seated person slips downward. Such a slip is uncomfortable and may give the seated person anxiety when the seated person needs a nursing care or is corporally and/or mentally weak such as an aged person, a disabled person, and a hospitalized person or the like.
Especially as shown in FIG. 7(a), when the seated person sits shallowly, this slip becomes larger as shown in FIG. 7(b). When there is a skin trouble (for example, a bed sore, a burn injury, an inflammation, or the like) on the back of the seated person or near his/her waist 106, the slip gives the seated person aches and pains.
For example, when services of a shampoo are going to be supplied to the seated person by a hairdresser/barber, the entirety of the chair must be inclined downward rather than the tilted postures of FIG. 6(b) and FIG. 7(b) to arrange his/her head 109 backward on a shampoo bowl.
In such a case, the slip gives the seated person discomfort and/or anxiety. Furthermore, a nurse or the hairdresser/barber must support the body of the seated person with hands, and must move his/her head to reach on the shampoo bowl when the seated person is not a healthy person. Such work is very hard. The hairdresser/barber cannot begin his/her services immediately, thereby increasing waste of time.
When the head of the seated person is going to reach on the shampoo bowl, a situation changes from those of FIG. 8(a) and FIG. 8(b) to that of FIG. 8(c). The seated person may feel pain rather than discomfort since his/her legs are extraordinarily lifted up. This posture is very dangerous especially when the seated person has a hypertension, aftereffects of a stroke, or the like.
As shown in FIG. 9(a), Document 1 (Japanese Patent Application Laid-Open No. 2001-149413) discloses a technique of dividing a seat into a set of a forward seat part 110 and a backward seat part 111, and foldably connecting these seat parts 110 and 111 with a hinge 112. As shown in FIG. 9(b), this enables to fold the backward seat part 111 downward as the backrest 101 is gradually inclined backward, thereby slightly improving the problems caused by the above-mentioned slip.
As discussed above, when the backrest 101 is inclined greatly backward as shown in FIG. 9(c) like in a case where the hairdresser/barber is going to supply services of a shampoo to the seated person, the knees 105 are raised to form clearances from the thighs 103 and/or the lower legs 104 to the forward seat 110. Therefore, the lower body of the seated person becomes unstable to cause discomfort. Since the legs are extraordinarily lifted up as the same as FIG. 8(c), there is a danger as the almost same as that of FIG. 8(c).    [Document 1] Japanese Patent Application Laid-Open No. 2001-149413    [Document 2] Japanese Patent Application Laid-Open No. 2004-141247